I have a Wacom Intuos Pro. In LRC 10, I could use the back of the pen ("eraser") to temporarily switch the brush tool from A or B to Erase. This functionality seems to have broken with the update to LRC 11 when using the updated Mask tool. When I use the back of the pen now, it just adds to the brush stokes instead or erasing them.
Updates to the Adobe Photography Products were released today and contain a fix for this issue. Please install the update via your Creative Cloud Desktop App or your respective App Store. Note: You may need to refresh the Creative Cloud App for desktop software to show an update available. ([Ctrl/Cmd]+[Alt/Opt]+ [ R ]) For Mobile downloads, it may take several days for the update to appear in your respective App Stores. Thank you for your patience.